This invention relates to the detection of magnetic fields.
There are several commonly known techniques for sensing or detecting magnetic fields. Perhaps the oldest known technique is the one employing a permanent magnet. Other exemplary approaches involve second harmonic detection or the flux reset type detection. The principle of a majority, if not all, second harmonic detectors is to provide a magnetic path to the external flux to be detected and to vary the reluctance of this path to change the amount of external flux flowing through the magnetic circuit. See for example U.S. Pat. No. 2,786,179 and my U.S. Pat. No. 4,059,796, both assigned to the assignee hereof. For an example of flux reset detection see U.S. Pat. No. 2,390,051.
Nevertheless, herein is disclosed an approach to magnetic field detection which, it is believed, has heretofore gone unrecognized. More particularly, in accordance with the present invention, the differential phase lag of induced flux, relative to the magnetization field, caused by the steady state field component to be detected, provides an indication of said field to be detected.